Paper on the Environmental Process of Coastal Erosion
The environmental process of coastal erosion has long been the subject of environmental management; particularly because it directly threatens human assets and wellbeing over relatively short time scales. Coastal erosion is significant because 44% of the worlds population live within 150km of the coast (Cohen et al., 1997 cited in Brommer et al., 2009: 181), and with it millions of dollars worth of trade, tourism, assets and business. Many environmental processes need thorough identification of ecosystem services, a process of valueation which often hinders the application of urgently required management. However, with the vast value of coasts already acknowledged, we can examine how well this has translated into investment in the form of research and response. This essay will explore past approaches to coastal management, and its effectiveness in addressing the coast as an open system with complex human interactions.
In order for an environmental process to be managed, a value has to be attached to it. Coastal land is valued mostly in the form of investments in infrastructure, business, housing and tourism facilities established largely due to locational advantages through ocean access routes. This mass investment has often transformed coastal areas into urban environments; largely stagnant establishments in comparison to the dynamic nature of coasts. Because of a particular perspective on where coastal value lies, the adaptive capacity of highly developed coasts is greatly reduced (Leafe et al., 1998). This has lead to the common command and control approach rather than a focus on working with the process of coastal dynamics. There is a lack of appreication that many environmental services and assets on the coast are best maintained by allowing them to change with the processes of coastal dynamics (Leafe et al., 1998: 287). Such assets offered by coastal systems include the creation and maintenance of habitat which fosters biodiversity. As a beach system undergoes natural erosion, rather than reducing beach size the whole beach system is translated inland along with the habitats associated with it. Hard engineering such as sea walls have been a common response to such translation in the past, however by saving the land behind the wall, the beach itself is sacrificed. Value is given to land behind the shoreline, rather than the coastal processes themselves. Like many environmental processes, coasts are only valued if a financial benefit can be gained.
In order to manage any environmental system, an understanding of the processes involved in the system is crucial (Leafe et al., 1998: 282). What this incorporates for the coastal system is the acknowledgement of it’s broad scale and interconnectedness and the ability to identify where human and natural systems intersect. For many decades up to the 1980s coastal management took the form of hard engineering with the ad hoc situated command and control approach (Barrow, 1999: 20 and Leaf et al., 1998: 282). Such responses are usually informed by the current research and science available at the time, or the lack there of in the instance of coastal mangement. Limited understanding particularly in coastal evolution has meant management has been highly reactive and not appreciative of the natural timescales of coastal change. Research into beach profiles has since revealed trends in coastal dynamics which are characterised by short periods of rapid erosion followed by long periods of recovery and sediment accumulation. By responding only to short-term storm cut erosion, management in the past has ignored the decadal scale of erosion and accretion cycles. These cycles may infact restore or extend the beach in the long term but include phases of erosion also. We cannot infer an overall direction of coastal movement from instantaneous events. Ad hoc schemes implemented in the past that were driven by these events were based on site and time specific studies. These schemes had the potential to solve the issue locally but without consideration of the wider implications on a wider spatial scale and longer time scale (Leafe et al., 1998: 282). A greater understanding of three key controls present in naturally functioning coastlines has led to transformations in how coastal management is approached. These are sediment supply, wave processes and sea level. Attempts to understand these three major components of the coastal system include the sediment budget approach, sediment cells, wave and storm hydrodynamics and studies of coastal evolution.
Any issue of erosion can be associated with sediment supply. Coastal material works to protect the beach through the alternation of swell and storm profiles. Under high energy, erosive conditions beach material is drawn offshore to form a bar which reduces water depth and hinders waves’ ability to translate erosive energy onshore. Sediment needed for this is usually supplied from weathered cliff materials and fluvial inputs which are transported by long shore currents; any reduction in this will hinder the adaptibility of the beach under varying energy conditions. One way in which research has attempted to conceptualise this is through sediment budgets which quantify a balance between sediment input and output within a coastal area (Cooper and Pethic, 2005: 116). Any surplus in sediment is likely to lead to depostion and beach accumulation whilst a deficit will likely result in erosion. With this knowledge we can identify processes within the coastal system which may intersect with anthropogenic processes; schemes may then be put in place to manage these interactions.
To display this we will consider erosion along West Africa between Ghana and Nigeria. The overriding trend along the coast here is trangressive with long shore drift flowing from east to west (Ly, 1980). A large temporal scale analysis of this coast’s evolution may infact reveal coastal defence as uneconomical due to processes such as subsidence constantly working to raise relative sea level. The Volta river is situated on the Eastern end of Ghana’s coast and pre 1961, when the Akosombo dam was built, sediment from a drainage basin of about 390,000 km2 supplied the eastern flowing long shore drift (Ly, 1980: 326). Since dam construction, only 0.5% of the catchment’s sediment is able to reach and be transported along the coast. In response to this loss in material, a breakwater was installed at Lome causing interuption to natural coastal processes. This combined with the loss of sedimet from the Volta lead to erosion rates of up to 10m per year down drift of Ghana. This can be seen along the Keta coast since dam construction in 1961 where rates of erosion increased by between 33 and 66 percent (Ly, 1980: 331). This has lead to the loss of vital tourist and resort beaches and damaged infrastructure such as Ghana- Benin highways during storms such as those experienced in 1984. It can be seen that a site specific, ad hoc approach to coastal management in the past has treated the symptoms of erosion locally yet aggravated the system as a whole, affecting adjoining stretches of coast.
This example is archetypal of the lack of understanding which has left coasts either unconsidered or mismanaged. In the past, the role of social planning and broader considerations in environmental managment were not regarded and often saw the implementation of such ‘hard engineering’ (Leafe et al., 1998: 282). These include sea walls, groynes and other forms of rock armour which work to protect local property behind the beach by fixing land position and preventing processes such as shoreline change and littoral transport of sediment alongshore. As time has progressed, such management approaches have been exposed as unsustainable. Surfacing in the 80s and particularly in the 90s were ‘soft’ approaches to management attempting to work with, and enhance natural proccesses in the environment with measures such as dune stabilisation and beach nourishment. Since then environmental management has evolved into both a social and natural discipline seen particularly in integrated strategic approaches. These approaches focus on a more wholistic, interdisciplinary understanding of the wider social and natural regimes of the coast and incorporate public involvement and the consideration of non engineering solutions to management (Leafe et al., 1998). In the United Kingdom an integrated strategic approach was undertaken by the former Ministry of Agriculture Fisheries and Food in 1995 with the introduction of Shoreline Mangement Plans (SMPs) (New Forest District Council, 2001). This management initiative had a two stage approach consisting firstly of outlining objectives, research and analysis followed by a plan preperation phase (Leafe et al., 1998: 283). The first phase of analysis incorporates the social sciences through considerations of the human environment, such as the stake holders, land use, coastal defence issues, planning and the legal context in addition to considerations of the natural environment and coastal processes. The second phase identifies management units and determines the preffered Strategic Coastal Defence Options in order to compile a sustainable plan. Such an approach to SMPs incorporates greater understanding through the integration of social sciences. This transforms environmental management into managing how environmental and human processes interact on a global scale rather than controlling natural proccesses on an individual basis.
If this was applied to the case of West Africa pre 1961, insights into relative sea level rise and long shore drift may have prevented development along the coastal hazard zone aswell as maintained natural long shore drift. This highlights a key issue surrounding past coastal management: it is largely site specific and has not considered coastal processes as large interrelated systems connected to and influenced by human systems. A more wholistic approach which analyses both environmental and human context best equips planners to decide if and how to manage a coastline under the effects of erosion.
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